Electric heater



'R. P. BARNSTEML ELECTRIC HEATER. APPLICATION FILED ocr. 29. 1919.1,360,999. Patented Dec. 7, 1920.

Fig-.3 Tg2 Fly-ff Cl/ me UNITED STATES PATENT OFFICE.

ROBERT P. BARNSTEAD, OF BOSTON, MASSACHUSETTS.

ELECTRIC HEATER.

Application filed October 29, 1919.

To all 207mm t may concern.'

Be it known that I, ROBERT P. BARN- s'rEAD, of Boston, in the county ofSuffolk and Commonwealth of Massachusetts, have invented certain new anduseful Improvements in Electric Heaters, of which the following is afull, clear, and exact specifica tion.

One of the difficulties found to exist in connection with electric waterheaters is that which results in case the attendants omit to keep thesame supplied with water. The water having all boiled away, with theheater still in action, the receptacle is liable to become overheatedand also the solder uniting the heater units thereto,` and the entireapparatus injured and made useless, either permanently or until repairscan be made.

The object of this invention is the effecting of means whereby a degreeof heat somewhat in excess of that of boiling water but less than whatwill be injurious to the parts, can be made to break the electriccircuit to the heater units and thereby guard against injury.

To this end I prefer to form one of the electric terminals with afusible section such that when the excessive heat reaches it, the partswill separate and break the circuit.

In the drawings formingI part of this specification, Figure l is asectional elevation of a water receptacle having a single heater unittherein, and with the terminals of the heater unit provided with myimproved circuit-breaking device. Fig.2 is av side view of the fusiblyseparable terminal. Fig. 3 is a sectional view of the same. Fig.

4 is a view of parts thereof separated. Fig.

5 is an end view showing the manner in which a spring device acts toinsure separation of the arts after the fusible portion has melted. ig.6 is a side view of the same.

In Fig. 1, the water receptacle 1 is shown having a single heater unit 2therein of well known form, and rising from the bottom of thereceptacle. Depending from the lower end of the heater unit are its twoterminals 3 and 4 designed to plug into a hand-piece 5 of well knownconstruction 'oined by a cable 6 to a source of current.

he terminal 4 maybe of usual construction, but the terminal 3 is the oneembodying the main feature of my invention.

As shown in Figs. 2 and 3, the termmal Specification of Letters Patent.

Patented Dec. 7, 1920. Serial No. 334,265.

section T which communicates directly with the interior of the heaterunit, is provided with a threaded head 9, preferably formed with ashoulder l0, upon which threaded head is screwed the internally threadedthimble 11 having a flat outer end 12. The terminal 3 is also formedwith a flat end 13 somewhat enlarged diametrically, and between thesetwo flat surfaces is placed a wafer of easily fusible metal 14 suitablysoldered or fused to both. lVhile I have illustrated this fusible metalas though it were nearly an eighth of an inch thick, it is hardlynecessary to have it quite so thick, especially when my spring separatoris used.

This spring separator consists of a leaf spring 15 attached to the handpiece 5 near the socket which receives the terminal 3, and givesv aninward bend past the opposite margin of the terminal, as shown in Fig.6. Normally this spring rests against the thimble 11 and does not aHectthe opera" tion of the heater in any way so long as the fusible metalholds the parts together. But the instant any excessive heat melts thewafer 14 or otherwise causes it to release its hold upon either or boththe fiat surfaces 12, 13, then the spring 15 immediately acts to turnthe hand piece 5 on the terminal 4 as an axis until the terminal 3 isout of alinement with the thimble 11 and free of possible contacttherewith.

When it is found that the water receptacle is empty and the current cutout from its heater unit, it is the work of a moment only to unscrew thethimble 11, after pulling off the hand piece 5, and to screw on a freshthimble and attached terminal. The reapplication of the hand piece againswitches on the current, and the water which may now be poured into thereceptacle is soon set to heating.

If both terminals were made like the fusible one above described, thespring 15 would be unnecessary, since the hand piece would simply dropaway from the heater; but I prefer to have one alone thus made fusiblefor the purpose of halving the delay and expense of making the changeafter an overheating has occurred.

I find that by giving a twist to the cable 6 previous tothe applicationof the hand piece 5 to the terminals, this twist will serve to turn theterminal 3 away from possible contact with its thimble 11, without theem- Cil ployment of the spring l5, but l prefer to provide this springbecause so many attendants will forget to thus twist the cable.

That l claim is:

l. An electric terminal comprising a terminal member having a iiat end,a member having a flat end easily detachable from the circuit, and athin water of easily fusible metal uniting said flat ends.

2. The combination with a heater unit having terminals one ot which isformed with a threaded head, an internally threaded thimble screwed uponsaid head, a terminal member, and a body ot' easily fusible metaluniting the latter to said thimble.

'3. rlhe combination with a hea-ter unit having terminals one et whichis in sections, easily fusible metal uniting said sections, and a handpiece having a cable connected therewith, the hand piece heilig adapted'tor engagement with both terminals, said hand piece being adapted torevolve on one ot the terminals when the easily fusible metal oi' theother has melted.

4. rl`he combination with a heater unit having terminals one of which isin sections, easily fusible metal uniting said sections, a hand piecehaving a cable connected therewith and adapted for engagement with bothterminals, and a leaf spring attached to said hand piece and curved torest againstthe separable section and turn the sections out ot possibleContact with each other when the fusible metal melts.

ln testimony that l claim the foregoing invention, I have hereunto setmy hand this 27th day of October, 1919.

ROBERT l). BARNSTEAD.

